Cordless radiotelephones typically include a base station and a handset. The base station comprises of a transformer, an RJ11 phone jack, an antenna, hang-up mechanism and battery charging pads. The transformer converts 110 V AC, provided by a wall outlet, to 12 V DC thereby supplying power to the base station. The RJ11 phone jack is connected to a conventional wall mount connector which couples telephone signals between the base station and a public switched telephone network. The antenna enables wireless RF communication between the base station and the handset. The battery charging pads interface with corresponding contacts on the handset allowing the handset's battery to be recharged using power from the base station when the handset is stored on the base station.
When the handset battery is sufficiently charged, the handset may be removed from the base station and taken to a remote site. The remote handset may place or receive telephone calls by coupling an RF signal between the base station antenna and an antenna on the handset.
Hang-up mechanisms have been devised which secure the handset to the base station and align the battery charging contacts on the handset to the battery charging pads on the base station. It is desirable that the hang-up mechanism be useful when the base station is mounted in both a horizontal and vertical configuration. A hang-up mechanism used by Panasonic Inc. on cordless telephone model number KX-T3725 uses a convertible separate piece part which has two positions. In the first position, the piece part is attached to the base station for the horizontal mounting configuration. To use the base station in a vertical mounted configuration, the piece part is detached from the base station, rotated 180.degree., and reattached to the base station. In the second position, the piece part reveals a protrusion which secures the handset to the base in the vertical mounted configuration. A disadvantage of Panasonic's two position piece part is that if the piece part is lost, the handset cannot be secured to the base station in a vertical mounted configuration.
A mounting mechanism used by Uniden Inc. on model number XE-250 uses a permanent protrusion molded into the base station which interlocks with a corresponding recess in the handset. Although the protrusion cannot be lost, the range of motion to hang up the handset in a horizontal mount configuration is very limited.
A hang-up mechanism for a cordless telephone model number HT-5500 by AT&T Inc. uses a recessed impression in the base unit corresponding to the profile of the handset thereby aligning the handset charging contacts to the battery charging pads in the base station. The disadvantage of this hang-up mechanism is that the base station cannot be used in a vertical mounting configuration.
The three aforementioned examples of hang-up mechanisms by Panasonic Inc., Uniden Inc. and AT&T Inc. use a conventional connection between the battery charging pads on the base station and battery charging contacts on the handset. The battery charging contacts on the handset comprise of two essentially flat stationary pads disposed within the same surface. The battery charging pads in the base station comprise two conductive spring loaded pads protruding from the same surface. When the handset is positioned in the base unit, the battery charging pads in the base station mate with corresponding battery charging contacts on the handset thereby providing power from the base station to recharge the battery in the handset. The battery charging pads in the base station are retractable and provide sufficient pressure for an electrical connection and overcome any tolerance gap between the handset's battery charging contacts and the base station's battery charging pads. The handset's battery charging contacts typically retract the battery charging posts in the base station as a result of the weight of the handset.
A different battery charging system is used by Sony Inc. model number SPP-110. Two batteries are provided with the system, one battery may be placed on the base station for recharging while the second battery is in use with the handset. The battery within the handset cannot be recharged when the handset is stored on the base station. A spent battery is replaced with a fully charged battery from the base station and the spent battery is recharged by the base station. This interchangeable battery pack concept is inconvenient for the user of the radiotelephone if one battery pack is lost. The handset may be used only when the one available battery has been charged.
A cordless telephone sold by Southwestern Bell Telecommunications Inc. model number FF-1700 (Freedom Phone), has integrated the hang-up mechanism with the battery charging pads. The radiotelephone comprises two conductive hooked protrusions extending from the same surface in the handset which couple to two conductive spring loaded pads disposed in the same surface in the base station. When the handset is hung-up in the base station, the two conductive hooked protrusions deflect corresponding conductive pads in the base station thereby causing an interlocking hang-up and battery charging mechanism. Although the radiotelephone's integrated hang-up and battery charging mechanism seems to be a good idea at first glance, using the product is very cumbersome. Once the handset is secured to the base station, it can only be removed by applying a strong force in a particular direction. The release operation is so cumbersome that the manufacturer included special instructions in their user manual describing the procedure for removing the handset from the base station. Normally, this operation is so simple the user needs no instructions.
Therefore, a formidable challenge is to integrate the hang-up and battery charging mechanisms whereby the handset may be coupled to the base station over a wide range of motion in both a horizontal and vertical mounting configuration.